1. Field of the Invention
The present invention relates to an X-ray imaging apparatus including a transportable electronic cassette and a pedestal for supporting the transportable electronic cassette.
2. Description of the Related Art
In the field of medical imaging services or other imaging industries, X-ray photography has become widely used. In X-ray photography, an object is subjected to X-ray radiation, and thereafter an intensity distribution of X-rays transmitted through the object is detected in order to obtain an X-ray image of the object.
An example of a method for obtaining the X-ray image includes a film screen method. In the film screen method visible light emitted from a rare-earth phosphor, for example, which is sensitive to the X-ray, is photographed by a photographic sensitive film, and the photographic sensitive film is chemically developed to visualize the photographed visible light as the X-ray image.
Subsequent technical innovation has yielded various other methods to obtain the X-ray image. As one of the methods, there is a Computed Radiography (CR) method in which the above-described visualizing method of the film screen method is combined with digital technology in order to visualize the light. In the CR method, a latent image once stored in a fluorescent material is excited by laser light or the like and recorded as a visualized image by photoelectrically reading the latent image. The CR method requires an image reading processing and an image reading apparatus in addition to an imaging unit.
Another method for obtaining an X-ray image takes advantage of advances in semiconductor technology. More specifically, a Flat Panel Detector (FPD) has been developed using a flat sensor in which pixels, each including a minute photoelectric converter and a switching element, are arranged in a grid pattern. An advantage of the FPD is that a stable X-ray image can be obtained even if an X-ray exposure amount varies because the FPD has an extremely wide dynamic range. Another advantage of the FPD is that the X-ray image can be obtained in a time efficient manner without chemical processing. In comparison, the conventional photographic sensitive film must be transported and later developed chemically, which takes much longer processing times.
A conventional X-ray imaging apparatus is broadly divided into, according to the environment of use, a stationary cassette, which is disposed at a predetermined place such as a general imaging studio, and a transportable cassette, which can be freely transported. The FPD system also includes a transportable electronic cassette. However, as is similar to a case of the conventional film cassette, the transportable electronic cassette is required to be thin and light, to be attached to various kinds of pedestal, and to have a degree of freedom to be used in a plurality of photographing environments.
Generally, the electronic cassette uses a semiconductor sensor in a process of acquiring and outputting the X-ray image. To that end, the electronic cassette needs electric power for powering relevant modules such as the semiconductor sensor. The electronic cassette thus has a cable attached thereto for receiving power and controlling the relevant modules thereof from an external device.
However, handling the electronic cassette having the cable attached thereto is difficult because the cable used to deliver the necessary electric power may interfere with surrounding devices and prevent optimal positioning of the electronic cassette. Therefore, it is difficult for the electronic cassette with the cable to have the degree of freedom equal to that of the above described film cassette. In view of the above, a wireless electronic cassette is recently proposed, which can perform wireless communication with a photographing system control unit. The wireless electronic cassette includes a battery for supplying electric power instead of the cable.
In the wireless electronic cassette to which the electric power is supplied from the battery, a charged amount of the battery may limit a usable time period of the electronic cassette. As a result, a frequent change of the battery or a frequent charge of the electronic cassette by being connected to an external power feeding device may be required. Thus, a wireless electronic cassette powered by a battery may have difficulty in satisfying a demand that the electronic cassette be applied to a wide variety of photographing environments.
In view of the above, if the photographing is to be performed continuously and for a long period of time so that a plurality of image frames are obtained, it is desirable that the photographing be performed while the power is being supplied to the imaging unit through the external device.
Japanese Patent Laid-open No. 2005-006979 discusses a system in which a power feeding path of the battery or the external power source, or a wired or a wireless communication method is controlled according to a detection result of whether or not a cable is connected to the imaging unit. Further, in the imaging unit is provided with an electrode on an external surface, the electric power is fed from the external unit to the imaging unit through the electrode. In this arrangement, the imaging unit can be disposed in a direction the imaging unit matches to a position of a power feeding mechanism with ease by providing the power feeding mechanism to a holder, which position is securely fixed.
As described above, an X-ray imaging unit can be applied to variety of photographing environments. However, when photographing is performed with the imaging unit attached to a pedestal or the like, the imaging unit is not always positioned in a predetermined direction. Instead, the imaging unit is preferably moved to a desired position or in a desired direction. As a result, an applicable range of the imaging unit in photographing becomes remarkably wider. For example, in a case of the imaging unit having a rectangular imaging area, a diagonal direction of the imaging unit is matched to a longitudinal direction of the imaging area by moving the imaging unit to a desired position or in a desired direction, so that a wider range of photographing can be realized in one photographing event.